According to the publication, at the ripe, young age of just 20-years-old, Jenner has amassed $900 million ($A1.2 billion) since launching her cult beauty brand, Kylie Cosmetics, less than three years ago. This makes her the youngest person on the fourth annual ranking of America's Richest Self-Made Women.

By comparison, her 37-year-old sister Kim Kardashian-West - and arguably the most famous of the Kardashian-Jenner family - is worth an estimated $350 million ($A475 million).

And that's just the beginning. Forbes estimates that within the next year, Jenner will be the youngest self-made billionaire ever, male or female, trumping Facebook founder Mark Zuckerberg, who became a billionaire at age 23.

Snapchat founder Evan Spiegal also became a billionaire in his early 20s, but it will be Jenner who will surpass these social media magnates - and by using their platforms to grow her business and brand.

"Social media is an amazing platform," Jenner told Forbes about her brand strategy.

But while such huge success at such a young age would usually be lauded, the reaction to Jenner's cover has been anything but for the most part, with people calling the reality TV star and Forbes out on the "self-made" description.

A proper self-made entrepreneur, critics have argued, wouldn't rely on family wealth and an existing brand to launch their own venture. Or, as Dictionary.com cheekily tweeted, "self-made" means "having succeeded in life unaided".

Forbes calling Kylie Jenner a self-made billionaire when she was born into extreme wealth that most people will never even be adjacent to pic.twitter.com/1SF9f8BGRy